Vigorous research efforts are being made recently in the field of a mobile phone-purpose camera module, a digital still camera (DSC), a camcorder, and a PC camera (an imaging device attached to a person computer) all connected with an image pickup system. One of the most important components in order that a camera module related to such an image pickup system obtains an image is an imaging lens producing an image.
Recently, an optical lens system is constructed by using 5 pieces of lenses for compactness and low cost. Each of 5 pieces of lenses is comprised of lenses with a positive (+) refractive power and lenses with a negative (−) refractive power.
However, although the 5-piece lens system may be advantageous in price, but in some cases, an image module of the above-mentioned structure fails to show satisfactory optical properties or aberration properties, and thus a high resolution imaging lens having a power structure is required.